1. Technical Field
This invention relates generally to the fields of metal forming and metal-forming tools such as pyramid rollers, tube-bending machines, and the like. It relates more particularly to an electrically powered portable tube bender that eliminates the need for a hand crank without otherwise significantly affecting tube bender operation.
2. Description of Related Art
The term “tube bender” herein refers to a tool used to form a bend in a metal tube or other length of stock. It bends the length of stock under operator control between opposing spaced-apart rollers to form a controlled radius with minimum twist (i.e., minimum distortion in the cross section of the stock as viewed in a plane perpendicular to the axis of elongation). Bending a length of stock that way is sometimes referred to as “air bending” (as opposed to “mandril bending”) and it has been in use since at least as far back as the early days of metal-tired wagon wheels. Nowadays, such air bending has found many more uses, even being used for metal railing and other decorative objects.
Some air-bending people perform many tube-bending tasks with a “portable” tube bender. Hawke Industries of Sun City, Calif. manufacturers one such manually powered portable tube bender as its “Gate Pro 3-Inch” model for tubes measuring up to about 3 inches by 3 inches and up to a 0.120-inch wall thickness. It is a portable apparatus in the sense that it weighs less than about one hundred twenty pounds, a weight one or two workers can manage to move about manually. Weighing in typically at about eighty pounds with overall dimensions on the order of about twenty-four inches high, forty-eight inches long, and eight to nine inches wide, the Gate Pro 3-Inch tube bender does not rely on a massive framework to withstand twist-producing asymmetrical forces. It relies, instead, on a carefully designed combination of parts in a symmetrical configuration.
The framework of the Gate Pro 3-Inch tube bender includes two uniformly spaced apart, 0.25-inch thick, steel framework members disposed in plane symmetry on opposite sides of a longitudinally extending vertical reference plane. The two framework members support three rollers on three separate and parallel rotational axes, with the three rollers being rotatably mounted on shafts (axles) that span the two spaced-apart framework members. In operation, the user rotates the uppermost roller (i.e., the centrally disposed main roller) by turning a crank attached to the main roller axle. As the user does so, rotation of the uppermost roller feeds the length of stock longitudinally through the space between the two spaced-apart framework members so that the stock travels intermediate the uppermost roller and the two lower rollers. In conjunction with that operation, the user adjusts the height of the uppermost roller on the framework in order to apply a desired downward force on the stock being bent, a downward force that is opposed upwardly by the two lower rollers. That action results in a bend in the stock having a desired radius that is dependent on roller spacing and the downward force applied by the uppermost roller.
Although such portable tube benders are effective in many respects, manual cranking involves extra physical effort and attention by the user beyond that required to carefully guide the length of stock through the apparatus while adjusting the uppermost roller. Thus, there is room for improvement.